"Air pollution is known to be associated with worsening asthma symptoms, but sometimes changing routines with regard to exposure to air pollution can have a positive effect," said senior study author Chris Carlsten, an associate professor at the University of British Columbia in Canada.

The woman described in the study improved her asthma once she and her doctor determined her bike route to work was taking her on a more polluted road than necessary.

"This experience shows that allergists can integrate their knowledge of the effects of air pollution into individual patient care, particularly asthma action plans," Carlsten added.

After the woman's bike route was analyzed, it was determined that 70 percent of her commute was in close proximity to major roadways.

Her doctor recommended an alternate route by which only 15 percent of her route was within 300 metres of high-traffic roads.

By following the new route over the next month, her asthma symptoms improved.

The study appeared in the journal Annals of Allergy, Asthma and Immunology.